Crossing gate control circuit

ABSTRACT

A control system for a highway crossing gate has been provided having circuit means for selectively operating the gate to open and closed positions when a signal of one or another polarity is present respectively. The improvement for providing directional control of the gate includes a plurality of polarity sensitive devices for selectively including or not including a resistor in the operating circuit of the gate in accordance with the polarity of the signal impressed on the operating circuit.

United States Patent [72] inventor J. Donald Hughson Macedon, N.Y.

[21 Appl. No. 856,963

[22] Filed Sept. 11, 1969 [45] Patented Aug. 24, 1971 [73] Assignee General Signal Corporation Rochester, N.Y.

[54] CROSSING GATE CONTROL CIRCUIT 3 Claims, 2 Drawing Figs.

[52] U.S.Cl 246/125, 317/11, 318/293 [51] lnt.Cl B611 29/08 [50] Field ofSearch 246/125, 238, 244, 219; 49/49; 3 1 8/293, 266; 317/11; 307/138 [56] References Cited UNITED STATES PATENTS 2,254,043 8/1941 Lynn 2,595,024 4/1952 Toulon 317/11 X 2,912,632 11/1959 Turtil 318/293 X 3,038,991 6/1962 Swanton 246/125 Primary ExaminerArthur L. La Point Assistant ExaminerGeorge H. Libman Altorney-Harold S. Wynn ABSTRACT: A control system for a highway crossing gate has been provided having circuit means for selectively operating the gate to open and closed positions when a signal of one or another polarity is present respectively. The improvement for providing directional control of the gate includes a plurality of polarity sensitive devices for selectively including or not including a resistor in the operating circuit of the gate in accordance with the polarity of the signal impressed on the operating circuit. 1

PATENTEU AU624 I971 SHEET 2 0F 2 NQE CROSSING GATE CONTROL CIRCUIT BACKGROUND OF INVENTION The invention relates to highway crossing gates and in particular to the electrical circuits for controlling the gate drive and latching mechanism.

Prior art devices are quite large because of the necessity for a heavy duty switching relay which when used with associated motor control apparatus, is required to handle high currents. That is, in a motor having field and armature windings, reversal of motor rotation is achieved by switching the polarity of either winding. When, however, an energized motor winding is open circuited, the magnetic field associated with it collapses, causing a current to be generated. If a relay is used as a switching device, this current manifests itself at the contacts of the relay by a strong spark. The relay must therefore be a heavy duty type in order to be able to handle the current, without burning out its contacts. The type of relay necessary is quite cumbersome and rather expensive. It is desirable to eliminate the necessity of such a relay thereby reducing space requirements and overall cost of the system.

It is therefore an object of the invention to provide for a more reliable and economical gate control circuit.

Another purpose of the invention is to provide for a more compact and efficient design.

Still another purpose of this invention is to provide for an improved switching circuit.

SUMMARY or INVENTION An improved crossing gate control system has been provided for operating a crossing gate to open and closed position in accordance with selective energization of the operating circuit of the system with signals of one polarity or another respectively. The improvement for providing directional control includes a plurality of polarity sensitive devices for selectively including or not including a resistor in the operating circuit of the system in accordance with the polarity of the signal impressed on the operating circuit.

FIG. 1 is a block diagram of the control system of the present invention.

FIG. 2 is a detailed circuit diagram of the control system of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT A description of the operation of the system is described with reference to FIG. 1. Detector 3 senses the presence of a train at or in the vicinity of highway crossing HC and transmits the signal to switching control 4 for establishing the proper polarity for control circuit 5. The motor 6 responsive to control circuit drives the gate arm 9 through transmission 7 and shaft 8. The gate arm 9 is driven by motor 6 between a horizontal or warning position and a vertical or all-clear position. The gate 9 and latch are gravity biased for fail-safe operation; that is, in the event of a power failure, the latch 10 releases the shaft 8 and the gate 9 rotates from the vertical to the horizontal position so that oncoming motorists are prevented from crossing the tracks. Under normal conditions, however, latch 10 is energized by power from controller 11 and control circuit 5 holding shaft 8 in a predetermined position corresponding to a vertical gate arm position. The control circuit 5 and controller 1 I operate latch 10 for unlocking shaft 8. The gate is assisted in its downward motion by means of motor 6. The motor 6 also drives the gate arm 9 up by means of another circuit path in controller 11 as will be explained more fully later inthe discussion. Controller 11 is responsive to the angular position of shaft 8 and a corresponding gate arm 9 angular position. The control circuit 5' which is responsive to controller 11 is thereby synchronized with the position of gate arm 9 for a proper cycle of operation.

The operator of the controls of FIG. 1 is explained in detail with reference to FIG. 2.

The detector'3 consists of conventional track circuit 20 and 20' controlling interlocked track relays 21 and 22. The relays 21 and 22 control contacts 23 and 24 respectively. If the train enters track circuit 20 from left to right, relay 21 is deenergized, open-circuiting contact 23 deenergizing switching control 4.

The switch control 4 consists of a relay 25 controlling contacts 26 and 27. The contacts 26 and 27 provide for proper polarity of input leads 28 and 28' to control circuit 5.

Controller 11 includes switches3l through 34, shaft 12 and cams 13 mounted thereon for operating switches 31 through 34 at predetermined intervals corresponding to particular angular positions of gate arm 9 during its operational cycle. The correspondence between gate arm 9 and shaft 13 is accomplished through shaft 8 which directly drives gate arm 9 and also drives shaft 13. Each of the switches 31 through 34 has a legend noting in degrees the periods during which each of the switches is closed. For example, switch 31 is closed while the gate arm 9 is in any position between 50 and from the horizontal. This is necessary so that the gate 9 position can be synchronized with the circuit control 5 for proper operation of the various functions of the control system.

The first and second signal paths of the system are those paths which conduct signals of the first and second polarity respectively. The first polarity is shown at conductors 28-28 when switches 26 and 27 are at the back contacts and the second polarity is shown at the same conductor when the switch 26 and 27 are at the front contacts. Further, in the discussion, as the specific circuits are functionally described the first and second signal paths will become apparent.

The control circuit 5 includes relays P and H which operate together to activate and hold the latch 10 in its proper position for locking the shaft 8. As simply as possible, the latch 10 can be described as a ratchet device'15 slipping into notches 16. The ratchet 15 is responsive to relays P and H through linkage 12.

As the train enters track circuit 20 as indicated previously, relay 21 is deenergized open-circuiting contact 23 and subsequently deenergizing relay 25. Deenergization of relay 25 reverses the polarity of input leads 28 and 28. Upon a switching of contacts 26 and 27 to their back contact positions, the motor 6 begins to operate forward to lower the gate arm 9. A forward energy circuit for motor 6 is traced as follows from positive energy, the back contact of 27, lead 28 to motor 6 through switch 31 closed between the vertical position 90 and the 50 position, variable limiting resistor 30, forward bias diode 29 and to negative energy at back contact 26 through lead 28. It should be noted in this connection that diode 39 is also forward biased with respect to current in lead 28 and therefore current bypasses the armature of motor 6. This is done to provide for dynamic braking when switch 31 opens. Since gate arm 9 is gravity biased it does not require much energy to move the gate arm 9 from the vertical to the horizontal position, so the power bled off lead 28' through diode 39 does not affect the operation of the system substantially when switch 31 is closed. Limit resistor 30 is used to adjust the current in motor 6 during the drive down cycle and thereby controls the speed of motor 6.

When switches 26 and 27 are moved to their back contacts, relay H drops latch 10 and unlocks shaft 8. This occurs because diode 37 is reverse biased with respect to the polarity of switches 26 and 27 at their back contacts. The relay H sees the reverse biased diode 37 as an open circuit and therefore is deenergized, thereby disengaging latch 10.

As the motor rotates and drives the gate 9 down, it reaches the 50 mark above the horizontal and at this point switch 31 open-circuits the motor 6 circuit. However, since the gate arm 9 is gravity biased, it continues to fall towards the horizontal. The energy produced by the moving gate arm is transmitted through the shaft 8 and transmission 7 to motor 6 and drives motor 6 as a generator. The diode 39 is forward biased with respect to the current generated in motor 6 and permits current to pass through snub resistor 40 back into the circuit for motor 6 along wire 41. Resistor 40 is adjustable and the force that the motor 6 exerts opposing the falling of gate arm 9 can be adjusted by increasing or decreasing the resistance 40. An increase in the resistance will decrease the current and thus the backward force of motor 6 on gate 9. This decrease in backward force allows for an increase in the speed of the gate arm 9 towards the horizontal position. When the gate arm arrives at the 5 mark above horizontal, resistor 40 is shunted out by wires 43 and 42 through switch 33. The total current generated by motor 6 is then increased creating a strong back force and thus slows the gate arm 9 down considerably causing it to come to a gentle stop at the horizontal warning position.

As the last car of the train passes the highway crossing I-IC, relay 2] is endrgized closing contact 23 completing the circuit for energizing relay 25 and switching the contacts 26 and 27 back to their front contacts. Relay 22 remains up because of the interlock with relay 21. Immediately a circuit is complete for reversing the direction of motor 6 from positive energy through front contact 26 along wire 28 and 44 through forward bias diode 45, switch 32 closed between the horizontal position 0 and 80 in controller 1 1, wire 41, through motor 6, and back to negative energy at front contact 27 through wire 28.

In this situation, both the resistors 30 and 40 are eliminated from the control circuit because of the use of diodes 29 and 39. It is desirable to have all the positive power delivered to the motor 6 so that the gate arm 9 can be raised quickly against the gravity bias. This is accomplished by eliminating limit resistor 30 by reverse biasing diode 29 and shunting around that resistor through diode 45 which is forwarded biased with respect to the polarity of input terminals 28 and 28', through switch 32 and wire 41 to motor 6. Diode 29v is reverse biased with respect to the positive polarity of input terminal 28 provided by closing front contact 26 and therefore eliminating resistor 30 from the circuit of motor 6. The diode 39 is reverse biased with respectto the negative polarity of wire 28' delivered through front contact 27 and therefore open-circuits resistor 40 from its shunt across motor 6. By using these diodes, change from forward to reverse of the motor can be accomplished by means of a single switching control 4 and without the necessity for heavy duty switching apparatus.

When contacts 26 and 27 are switched to their forward contacts, relay H is energized, however, it is merely a holding relay and cannotengage latch alone. In order to provide for an activation of latch 10, relay P is incorporated in the circuit. Contact 34 is closed as the gate arm 9 is between the 76 and 85 position on its upward swing. The relay P is energized from the circuit of motor 6 along wire 42 through switch 34 and wire 46 through the coil of relay P, diode 37 to negative energy along wire 28' and front contact 27. During this phase of operation, relays P and H energized together activate latch 10 through linkage 12. As the gate arm passes 85, P is deenergized. Relay H is powerful enough, once assisted, to hold the latch 10 activated in order to lock the shaft 8. The gate arm continues upward towards the vertical position and reaches the 88 mark opemcircuiting switch 32 and disconnecting motor 6. The momentum of the gate arm 9 carries it up to the vertical 90 position and it is locked by latch 10.

The insertion of diodes 29, 37, 39 and 45 provides reliable and safe operation of the gate arm 9 by means of simple and inexpensive circuit elements. These diodes provide for simplified switching from one mode of operation to another without the necessity for complex and heavy duty switching apparatus.

A motor having both a field and armature winding may be used in an alternate form of the invention. In FIG. 2, a field winding would replace shunt wire 41 in the schematic. However, it is contemplated that in the preferred embodiment, motor 6 is a permanent magnet motor which is included for reducing initial cost, ease of installation and reduction in maintenance costs.

Light and bell warning signals usually associated with a crossing gate signal are not included because they form no part of the present invention. However, inclusion of contacts in controller 11 for determining at which times the various light and bell warning signals shall be activated can easily be accomplished and such wiring schemes are well known in the art.

While there has been shown what at present is considered to be a preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the true spirit and scope of the invention.

lclaim:

1. An improved control system for operating a railroad highway crossing gate comprising:

a detector, coupled to the rails for generating an output signal indicative of train presence,

a switch means, responsive to said detector producing signals at its output of a first polarity when the signal indicative of train presence is received from the detector, and producing signals at its output of a second and opposite polarity when the signal indicative of train presence is absent;

a driving means responsive to the signals produced by said switching means for operating the gate forward to a horizontal position when the first polarity signal is received and reverse to a vertical position when the second polarity signal is received, wherein the improvement for providing directional control comprises;

a forward current path coupled to the driving means for conducting signals of the first polarity to the driving means including:

a first diode, said diode being forward biased with respect to said first polarity signal, for conducting said signals of the first-polarity, and reverse bias with respect to signals of the second polarity, for blocking the signals of the second polarity, and

a variable resistor serially connected between said first diode and the driving means for controlling the signals of first polarity conducted to said driving means;

a reverse current path coupledto said driving means for conducting signals of the second polarity to said driving means for reversing said driving means including:

a second diode forward biased, with respect to said second polarity signal for conducting said signals of second polarity, and reverse biased, with respect to to said signals of the first polarity, for blocking said first polarity signals from said driving means,

a latch responsive to the second polarity signal for locking said gate in a vertical position, said gate being gravity biased and tending to rest in the horizontal position when the second polarity signal is absent; and a further improvement comprises:

a second reverse current path for directing signals of the second polarity to said latching including;

a third diode forward biased with respect to said second polarity signal for conducting said signals of said second polarity to said latch and reverse biased with respect to the signals of the first polarity for blocking said first polarity signals from said latch.

2. The improved control system of claim 1 wherein the driving means comprises:

a permanent magnet motor, said motor responsive to the first and second polarity signals and rotating forward for driving the gate down to the horizontal when it receives said first polarity signal and rotating reverse for driving the gate up to the vertical when said second polarity signal is received.

3. The improved control system of claim 1 further comprismg:

a controller coupled to the signal directional means including a plurality of switches operated at predetermined positions for the gate arm, each of said switches for opening and closing segments of the first and second signal paths, and conducting said first and second polarity signals to said driving means and said latch, thereby permitting the changing of the direction of operation of the crossing gate;

and a control circuit including;

a terminal of the drive means serially connected to said switches, for periodically opening and closing said drive means connection;

a limit resistcifserially connected to the first switch and the first terminal of the drive means for controlling the current to said drive means;

the second of said switches serially connected to the second diode at its anode for periodically opening and closing said connection;

a snubbing resistor serially connected with the second switch; I

a shunt connection joining the junctions of the motor and the first switch and the junction of the second switch and the second resistor;

the third of said switches connected across the snubbing resistor for periodically shunting out the snubbing resistor;

a first relay coupled to the latch for holding the latch in an activated mode;

a second relay for activating the latch in combination with the holding relay;

the first relay electrically connected to the junction formed by the first and second diodes;

the fourth of said switches serially connected between the third switch and the second relay periodically opening and closing said connection;

a junction fonned by a second terminal of the drive means and cathode of the third diode; and

a fourth diode connected at its anode to the junction fonned by the second terminal of the drive means and the cathode of the third diode, and connected at its cathode to the junction formed by the first and second relays, for limiting current flow only to the junction of the second terminal of the drive means and the third diode;

the junction of the first and second diode form one input terminal of the circuit, and the junction of the second terminal of the drive means with the anode of the third diode and cathode of the fourth diode form a second input terminal of the circuit. 

1. An improved control system for operating a railroad highway crossing gate comprising: a detector, coupled to the rails for generating an output signal indicative of train presence, a switch means, responsive to said detector producing signals at its output of a first polarity when the signal indicative of train presence is received from the detector, and producing signals at its output of a second and opposite polarity when the signal indicative of train presence is absent; a driving means responsive to the signals produced by said switching means for operating the gate forward to a horizontal position when the first polarity signal is received and reverse to a vertical position when the second polarity signal is received, wherein the improvement for providing directional control comprises: a forward current path coupled to the driving means for conducting signals of the first polarity to the driving means including: a first diode, said diode being forward biased with respect to said first polarity signal, for conducting said signals of the first polarity, and reverse bias with respect to signals of the second polarity, for blocking the signals of the second polarity, and a variable resistor serially connected between said first diode and the driving means for controlling the signals of first polarity conducted to said driving means; a reverse current path coupled to said driving means for conducting signals of the second polarity to said driving means for reversing said driving means including: a second diode forward biased, with respect to said second polarity signal for conducting said signals of second polarity, and reverse biased, with respect to to said signals of the first polarity, for blocking said firsT polarity signals from said driving means, a latch responsive to the second polarity signal for locking said gate in a vertical position, said gate being gravity biased and tending to rest in the horizontal position when the second polarity signal is absent; and a further improvement comprises: a second reverse current path for directing signals of the second polarity to said latching including; a third diode forward biased with respect to said second polarity signal for conducting said signals of said second polarity to said latch and reverse biased with respect to the signals of the first polarity for blocking said first polarity signals from said latch.
 2. The improved control system of claim 1 wherein the driving means comprises: a permanent magnet motor, said motor responsive to the first and second polarity signals and rotating forward for driving the gate down to the horizontal when it receives said first polarity signal and rotating reverse for driving the gate up to the vertical when said second polarity signal is received.
 3. The improved control system of claim 1 further comprising: a controller coupled to the signal directional means including a plurality of switches operated at predetermined positions for the gate arm, each of said switches for opening and closing segments of the first and second signal paths, and conducting said first and second polarity signals to said driving means and said latch, thereby permitting the changing of the direction of operation of the crossing gate; and a control circuit including; a terminal of the drive means serially connected to said switches, for periodically opening and closing said drive means connection; a limit resistor serially connected to the first switch and the first terminal of the drive means for controlling the current to said drive means; the second of said switches serially connected to the second diode at its anode for periodically opening and closing said connection; a snubbing resistor serially connected with the second switch; a shunt connection joining the junctions of the motor and the first switch and the junction of the second switch and the second resistor; the third of said switches connected across the snubbing resistor for periodically shunting out the snubbing resistor; a first relay coupled to the latch for holding the latch in an activated mode; a second relay for activating the latch in combination with the holding relay; the first relay electrically connected to the junction formed by the first and second diodes; the fourth of said switches serially connected between the third switch and the second relay periodically opening and closing said connection; a junction formed by a second terminal of the drive means and cathode of the third diode; and a fourth diode connected at its anode to the junction formed by the second terminal of the drive means and the cathode of the third diode, and connected at its cathode to the junction formed by the first and second relays, for limiting current flow only to the junction of the second terminal of the drive means and the third diode; the junction of the first and second diode form one input terminal of the circuit, and the junction of the second terminal of the drive means with the anode of the third diode and cathode of the fourth diode form a second input terminal of the circuit. 